Conventionally, an evaporation fuel treatment device is known which absorbs evaporated fuel generated in a fuel tank into a canister and purges the absorbed fuel to an intake system during operation of an engine. In particular, the evaporated fuel is sucked by the engine while it is temporarily collected by the canister thereby to prevent emission of the evaporated fuel into the atmosphere. In an engine in which such an evaporation fuel treatment device as just described is incorporated, the fuel injection amount or the intake air amount is controlled taking an evaporated fuel amount desorbed from the canister into consideration.
On the other hand, in recent years, a hybrid vehicle (PHEV, PHV) has been developed which travels principally using a driving motor while an engine is used auxiliarily. In such a hybrid vehicle as just described, in comparison with a vehicle in which only an engine is used as a power source, the operating period of the engine is short and opportunities in which evaporated fuel absorbed by the canister is purged are few. Therefore, a technology has been proposed by which a closing valve is provided on a passage that connects a fuel tank and a canister with each other and the closed state of the fuel tank is maintained as long as possible to suppress evaporation of fuel in and absorption of fuel into the canister.
For example, the internal pressure of the fuel tank tends to increase as the temperature in the tank increases and tends to decrease as the fuel amount decreases. Therefore, it seems recommendable to normally keep the closing valve in a closed state unless the internal pressure of the fuel tank exceeds a predetermined pressure. Further, if the internal pressure upon refueling into the fuel tank is higher than the atmospheric pressure, then there is the possibility that the fuel may flow back from a fuel supply port when a filler cap is opened. Therefore, also it seems recommendable to open the closing valve just before refueling is performed to depressurize the fuel tank (for example, refer to Japanese Laid-Open Patent Application No. 2015-081528 and Japanese Laid-Open Patent Application No. 2014-092069). By performing such controls as described above, evaporation of fuel in or absorption of fuel into the canister can be suppressed.
A pipe for refueling is provided for the fuel tank, and a fuel supply port at the tip end of the pipe is kept closed by a filler cap. Upon refueling, the filler cap is removed after a filler door is opened, and a fueling gun is coupled with the fuel supply port. If the refueling comes to an end, then the filler cap is attached and then the filler door is closed. The open state of the closing valve is maintained until refueling comes to an end and the filler door is closed, and, when the filler door is closed, the closing valve is closed. An open or closed state of the filler door is detected by a sensor provided in the proximity of the filler door (for example, refer to Japanese Laid-Open Patent Application No. 2015-123883). An output of the sensor is used not only as a trigger for closing the closing valve after refueling but also, for example, for indication for announcing an open or closed state of the filler door or indication for announcing a refueling possible state.
However, for example, if the sensor described above breaks down, then since the open or closed state of the filler door cannot be detected, indication for announcing a refueling possible state is not performed even if depressurization of the fuel tank is completed, and there is the possibility that this may degrade the usability. Further, where a configuration is adopted that the filler door is automatically opened after depressurization of the fuel tank, the filler door is sometimes open even if the sensor is broken down. In other words, there is the possibility that a situation may occur that the filler door is actually open although refueling possible indication is not performed, and there is the possibility that this may confuse an occupant of the vehicle.